Emerson E2 Time Scheduling and Holidays, How Schedules Work, Absolute and Relative Events

stant period of time that consists of one ON event and one OFF event. The PWM cell takes the PID percentage and turns the output ON for an equivalent percentage of the total pulse period. In other words, if the PID output is 60% and the pulse period is 30 seconds, every 30 seconds the PWM output will be ON for 60% of 30 seconds (18 sec- onds) and OFF for the remaining portion of the 30-second period. Once the period has ended, the PWM Cell reads the PID output again and the process is repeated.

11.14Time Scheduling and Holidays

Time Schedules are used for timed activation and deactivation of loads and for providing occupied and unoccupied building times for occupancy-driven systems (such as Sensor Control, Lighting, and HVAC).

There are four different types of schedules used by the

E2. Brief description of each of these are given below:

Master schedules are the main scheduling unit used by the E2. A master schedule consists of up to 15 sched- uled ON/OFF event pairs, which may be programmed to occur on any individual date and time or series of dates and times. Master schedules may also drive slave sched- ules.

Slave schedules are similar to master schedules, except their operation is driven by a master schedule. Slave schedules, generally, are alterations of the master schedule’s event times. The ON/OFF times in a slave schedule may take place either at specific defined times of the day or relative to the times given in the master sched- ule. For example, a master schedule may say: “The build- ing is occupied from 8:00 a.m. to 9:00 p.m.” while one of its slave schedules says “Dim the building lights 15 min- utes before the store closes.”

Slave schedules may also be mastered by other slave schedules to create a series of stacked schedules.

Holiday schedules are used to tell master and slave schedules that a special day or event is occurring. For example, master schedules and their corresponding slave schedules may be programmed with special holiday events, such as “Keep all lights off during Holiday x.” The holiday schedule’s job is to inform the schedules to which it is connected, “Today is Holiday x.”

Although holiday schedules are used exclusively by Time Scheduling applications, they are set up as individual applications separate from Time Scheduling. See Section 11.14.2, Holiday Schedules for more information.

Temporary schedules are technically not schedules but temporary override functions that may be made to

exist within an individual master or slave schedule. Tem- porary schedules are used to temporarily override the ON/ OFF instructions of an individual master or slave sched- ule. Generally, temporary schedules are only used for one- shot applications, such as keeping the lights on an extra hour for a single night. Temporary schedules override all other events within a master or slave schedule, including holidays.

11.14.1 How Schedules Work

11.14.1.1 Events

Master schedules and slave schedules consist of up to

15 pairs of events. Events are simple commands to turn the schedule output either ON or OFF at a particular time within a range of days. Events are usually programmed in pairs, so that during a specified range of days the schedule output can be turned ON and OFF at a particular time within the same day. However, events may be pro- grammed singularly (on OFF or one ON command per day). Events may be programmed to take place on any or all days from Sunday to Saturday. In addition, events may take place on any or all of four holiday (or “special”) dates, called HD1, HD2, HD3, and HD4. Holiday sched- ules are used to tell the master or slave schedules when these special dates occur.

11.14.1.2 Absolute and Relative Events

Master schedule events always occur at specific times of the day. In other words, when you program an event pair in a master schedule, you must specify two specific times of the day the events will occur. These types of events are called absolute events.

However, when programming event times in slave schedules, you may choose to enter event times that are relative to its master schedule’s ON and OFF times. These types of events are called relative events. They are pro- grammed not as absolute times but as amounts of time before or after its master schedule’s events.

For example, suppose a master schedule is set up to be ON at 8 a.m. and OFF at 9 p.m. every day of the week, and you wish to set up a slave schedule so that its output comes ON 15 minutes before the master comes ON and OFF 15 minutes after the master goes OFF. To do this, you would set up the slave schedule to come ON at -00:15 and OFF at +00:15 every day of the week. The slave schedule will automatically determine the correct ON and OFF times.

11.14.1.3 Temporary Schedule Events

Each schedule may also be given up to three pairs of temporary schedule events. These events start and end at specific days and times and do not continue past those dates (in other words, temporary events cannot be made to

11-42 • E2 RX/BX/CX I&O Manual 026-1610 Rev 13 14-SEP-2011